The invention relates to a paint spray gun.
To achieve optimal results with paint spray guns, it is extremely important to set the spray pressure so as to obtain optimal atomization at a good operating speed and high application efficiency. For a precise setting of the pressure or monitoring of the input pressure, a pressure regulating valve with a pressure gauge is often added at the air inlet. However, the operation of the spray gun is impeded by the pressure regulating valve and pressure gauge, which are usually attached to the underside of the gun handgrip.
The Sata company therefore developed a spray gun, for example, marketed under the name of xe2x80x9cSata jet RP, Digital,xe2x80x9d in which the pressure-sensing and pressure display device is built into the grip of the gun body. In this known spray gun, a connecting borehole is provided at the bottom end of the handgrip, from the compressed air supply borehole running through the pistol grip to a pressure gauge chamber placed in the handgrip. Through such an arrangement, however, only the gun air inlet pressure can be monitored, not the spray pressure adjustable through a valve system.
An object of the invention, therefore, is to create a spray gun that facilitates the sensing and display of the spray pressure using simple means.
The invention relates to a paint spray gun with a paint nozzle placed on a gun body, an air nozzle placed around the paint nozzle, a compressed air valve placed within a piston borehole in the gun body, a compressed air borehole running through a handgrip of the gun body to the piston borehole, and a pressure-sensing and pressure display device placed in the hand grip. For sensing and displaying the spray pressure, a tube is placed in the compressed air borehole at a distance from its inner wall. The tube forms, in the interior, a channel for the compressed air supply to a part of the piston borehole placed upstream of the compressed-air valve, and borders an intermediate space between its exterior and the inner wall of the compressed air borehole. The intermediate space is connected via a first connecting channel with a pressure chamber placed downstream of the compressed-air valve and via a second connecting channel with a pressure gauge chamber in the handgrip allocated to the pressure-sensing and pressure display device.
In the spray gun according to the invention, the compressed air can be conducted through the tube inserted into the compressed air borehole to the valve system that can be actuated by a trigger, while the intermediate space formed between the inner wall of the compressed air borehole and the outer wall of the tube can be used for a compressed air connection between a pressure chamber placed downstream of the valve system and a pressure-sensing and pressure display device integrated into the handgrip of the gun body. Through the intermediate space and easily manufacturable connecting boreholes, the spray pressure that can be adjusted through the valve system can also be displayed without connection channels that are expensive to manufacture.
The use of a digital display device that is normally activated only when a predetermined pressure threshold is exceeded has the advantage, through the design according to the invention, of longer battery life for supplying power to the display device, since pressure is displayed only when the trigger is actuated.
Other embodiments may include additional features. Thus, for example, the connection between the pressure chamber downstream of the valve system and the intermediate space can be produced in a technically simple manner through a first connecting borehole, shifted to the side of the mid-axis of the compressed air borehole, and which runs diagonally through outside the handgrip to the pressure chamber, and is connected in a middle region with the intermediate space. At its outer end, the first connection borehole is sealed through a ball or another suitable sealing element.
The connection from the intermediate space to the pressure gauge chamber placed in the gun grip may also be accomplished through a second connecting borehole that runs expediently from the inlet of the compressed air borehole diagonally through the handgrip to the pressure gauge chamber. In this way, the second connecting borehole need not be sealed by a ball or the like, as is necessary with the first connecting borehole. The first and/or the second connecting borehole are, in a further advantageous embodiment, designed at least partially as capillary boreholes. Through such a capillary, solvents used for cleaning the spray gun, or even lacquer or paint residue can be prevented from reaching the area of the pressure sensor and consequently impairing or hindering the proper gauging of the pressure.